Electric lamp



A. G. CARTER Jan. 4, 1944.

ELECTRI C LAMP Original Filed March 4, 1941 \nven'rov I Andrew G. Cafl'ex Patented 4, 1944 UNITED STATES PATENT OFFICE v smc'rarc LAMP Andrew G. Carter, Grand Rapids, Mich. V Original application Mach 4, 1941, Serial No; 322,100. Divided and this application June 10, 1942, Serial No. 446,437

2 Claims. (01. 176-16) This invention relates to electric lamps and more particularly to that type of an electric lamp having an elongated filament held under tension past said shadow casting wire and to concentrate as much light from the lamp that is possible within a confined area so that the resultant shadow upon the work will be as clear and distinct and well defined as possible. For this purpose a, lens is used adjacent the lamp and in order to utilize as much as the light rays as possible it is desirable to have the filament of the lamp located closely adjacent the lens which will then pick up the rays emanating from the filament through a considerable are greater than if the lens and filament were spaced further apart.

It is also desired to maintain the filament straight at all times'so that it can be kept in positive alinement with the shadow casting wire throughout its entire length.

This invention embodies details of construction and arrangement by which the foregoing desirable functions are proficiently attained as hereinafter more fully described and particularly pointed out in the claims, reference being had to the accompanying drawing, in which Fig. 1 is aside elevation of a lamp embodying this invention.

Fig. 2 is an enlarged cross section of the same on the line 2--2 of Fig. 1 also illustrating a, lens in operating position adjacent the lamp.

Fig. 3 is a fragmentary perspective view show? ing the construction of one of the filament tensioning springs, and

Fig. 4 is a fragmentary section illustrating the means for supporting one of the lamp conductors.

Like numbers refer to like parts in all the figures.

The lamp has an elongated transparent bulb I made of glass which preferably is a special quartz glass to withstand the extreme heat generated by the filament. This bulb I has the conventional screw threadedplug 2 common with ordinary incandescent lamps and a partial vacuum exists within the bulb l which may contain a gas as is ordinarily used in incandescent bulbs. The electric current which operates the lamp is conducted to the conductors and filament therein in the usual manner through the structure of the plug 2 to which the conductors are connected.

The upper electrode 3 extends substantially the entire length of the lamp and is provided at its end remote from the plug 2 with a socket 4 which fits over a tip 5 provided on the interior of the bulb I. This supports that end of the inner lamp structure. I

The second conductor 6 extends from the plug 2 and to it is connected one end of the filament l by suitable means such as a curved element 8: The opposite end of the filament I is provided with an anchoring conductor 9 and this is supported from the conductor 3 by a group of tension springs In. It will be noted that the filament I is located exceedingly close to one side of the bulb l.

The current is conducted to the filament through the conductors 3, 5, 8 and 9 and tension springs 10 and these springs and conductors have suflicient cross sectional area and therefore a greater conductivity than the filament so that they do not become overheated in conducting the current to the filament. However, the filament of course becomes incandescent and in that stage it is delicate and its tensile strength is not great. However, it undergoes a considerable change in length when heated but the springs I 0 keep it 2 under constant tension and therefore straight at all times and yield to accommodate the longitudinal expansion and contraction. It has been found more practical to use a plurality of springs for this purpose than to attempt to construct a single spring which would operate satisfactorily. Each of the springs I0 is quite flexible and will flex a considerable distance and still retain approximately the same tension but one spring having sufficient flexibility to operate satisfactorily would not have sufficient tension to keep the filament taut and therefore a plurality of light flexible springs is used whereby their combined tension is sufiiciently great to function properly and they all have the same considerable range offiexibility.

It is preferable to use fiat springs l0 and to conveniently attach them to the electrodes 3 and 9 at their respective ends, each of the springs I0 is twisted near each of its ends one quarter turn as at ii and then wrapped around the electrode in the form of an eye I 2 where it may be attached as by welding or brazing.

It will be seen that the lamp constructed as described has its filament closely located adjacent one side'ot the bulb where it may be brought into close proximity with the lens l5 so that a large part of the rays emanating from the filament will engage and pass through the lens having their direction diverted thereby into a long narrow beam which can be directed against the shadow casting wire of the guide line light. Furthermore, the utilization of a plurality of relatively light yieldable springs acts to hold the filament taut and in a straight line which may be adjusted to be parallel with the shadow casting wire butthis plurality of springs having substantially the same degree of tension throughout their entire flexing movements do not \at any point exert anexcessive amount of strain upon the filament.

The invention is defined in the appended claims and is to be considered comprehensive of, all forms of structure coming within their scope.

I claim:

1. An electric lamp comprising, an elongated light bulb, a plug at one end of said bulb having two electric contact members, an elongated conductor electrically connected to one 01 said contact members and extending lengthwise of said bulb, means for anchoring said elongated conductor to the end of said bulb remote from said plug, a second conductor electricallyconnected to the other of said contact members, an elongated filament extending lengthwise of said bulb and having one end connected to said second conductor and a group of leaf springs mounted on said elongated conductor and also connected to the opposite end or said filament, said filament being unsupported intermediate its ends.

2. The elements in combination defined in claim 1 in which said leaf springs are twisted near their ends and wrapped around said elongated conductor.

ANDREW G. CARTER. 

